Chapter 105 STORMWATER MANAGEMENT

Transcription

1 Chapter 105 STORMWATER MANAGEMENT ARTICLE I Chester Creek watershed General Provisions stormwater management district implementation Statement of findings. provisions (performance Purpose. standards) Statutory authority Brandywine Creek watershed stormwater management Applicability. district implementation Compatibility with other provisions (performance ordinance requirements. standards) Water quality requirements for ARTICLE II all areas of the Township. Definitions Calculation methodology Word usage Design criteria for stormwater management facilities Definitions. ARTICLE III Stormwater Management Plan Requirements Erosion and sedimentation requirements. ARTICLE V Inspections General requirements Schedule of inspections Exemptions Plan submission. ARTICLE VI Plan contents. Fees and Expenses Plan review General provisions Modification of plans Municipal stormwater Resubmission of disapproved management plan review fee. drainage stormwater management plans Expenses covered by fees Additional costs. ARTICLE IV Stormwater Management Provisions ARTICLE VII Maintenance Responsibilities General procedures for water quality and quantity control Performance guarantee Stormwater management Maintenance responsibilities. districts. 105:

2 105-1 CHADDS FORD CODE Maintenance agreement for Enforcement; additional privately owned stormwater project requirements. facilities Violation deemed a public Postconstruction maintenance nuisance. inspections Violations and penalties; additional remedies. ARTICLE VIII Prohibitions Appeals. Figure 4-1, Water Quality and Prohibited discharges. Quantity Control Drainage Prohibited connections. Plan Preparation Procedure Roof drains. Appendix A, Release Rate Map Waste disposal prohibitions. Appendix B, Stormwater Management Design Criteria Alteration of BMPs. Appendix C, Riparian Buffer ARTICLE IX Technical Reference Guide Enforcement and Penalties Stormwater Facilities Maintenance and Monitoring Right of entry. Agreement Notices of violations. [HISTORY: Adopted by the Board of Supervisors of Chadds Ford Township by Ord. No Amendments noted where applicable.] GENERAL REFERENCES Sewers See Ch. 95. Water conservation See Ch Subdivision and land development See Ch Zoning See Ch ARTICLE I General Provisions Statement of findings. The governing body of Chadds Ford Township finds that: A. Inadequate management of accelerated stormwater runoff resulting from development throughout a watershed increases flood flows and velocities, contributes to erosion and sedimentation, overtaxes the carrying capacity of existing streams and storm sewers, greatly increases the cost of public facilities to convey and manage stormwater, undermines floodplain management and flood reduction efforts in upstream and downstream communities, reduces groundwater recharge, and threatens public health and safety. B. A comprehensive program of stormwater management, including reasonable regulation of development and activities causing accelerated erosion, is fundamental to the public 105:

3 105-1 STORMWATER MANAGEMENT health, safety, welfare, and the protection of the people of the municipality and all of the people of the commonwealth, their resources, and the environment Purpose. The purpose of this chapter is to: A. Promote health, safety, and welfare within the municipality. B. Implement the requirements of the Chester Creek Stormwater Management Plan. C. Implement the requirements of the National Pollutant Discharge Elimination System Phase II (NPDES II). D. Incorporate existing stormwater management regulations from Chapter 110, Subdivision and Land Development, of the Code of Chadds Ford Township, and Ordinance No by minimizing the damages described in 105-1A of this chapter through provisions designed to: (1) Manage accelerated runoff, erosion, and sedimentation problems at their source by regulating activities that cause these problems. (2) Utilize and preserve the existing natural drainage systems. (3) Encourage recharge of groundwater where appropriate and prevent degradation of groundwater quality. (4) Maintain existing flows and quality of streams and watercourses in the municipality and the commonwealth. (5) Preserve and restore the flood-carrying capacity of streams. (6) Provide proper maintenance of all permanent stormwater management facilities that are constructed in the municipality. (7) Provide performance standards and design criteria for watershed-wide stormwater management and planning Statutory authority. The municipality is empowered to regulate land use activities that affect runoff by the authority of the Act of October 4, 1978, P.L. 864 (Act 167), 32 P.S et seq., as amended, the "Stormwater Management Act," and the Pennsylvania Municipalities Planning Code, Act 247, as amended Editor's Note: Ordinance No. 66 adopted the Township's prior stormwater management regulations and was rescinded by this ordinance.. 2. Editor's Note: See 53 P.S et seq. 105:

4 105-4 CHADDS FORD CODE Applicability. A. This chapter shall apply to all areas of the municipality. B. This chapter shall apply to permanent stormwater management facilities constructed as part of any of the regulated activities listed in this section. Stormwater management and erosion and sedimentation control during construction activities are specifically not regulated by this chapter but shall continue to be regulated under existing laws and ordinances. C. This chapter contains only the stormwater management performance standards and design criteria that are necessary or desirable from a watershed-wide perspective. Local stormwater management design criteria (e.g., inlet spacing, inlet type, collection system design and details, outlet structure design, etc.) shall continue to be regulated by the applicable municipal ordinances or at the Municipal Engineer's discretion. D. The following activities are defined as "regulated activities" and shall be regulated by this chapter: (1) Land development and/or redevelopment. (2) Subdivision. (3) Construction of new or additional impervious or semipervious surfaces (driveways, parking lots, etc.). (4) Construction of new buildings or additions to existing buildings. (5) Diversion or piping of any natural or man-made stream channel. (6) Installation of stormwater management facilities or appurtenances thereto. (7) Placement of fill material Compatibility with other ordinance requirements. Approvals issued pursuant to this chapter do not relieve the applicant of the responsibility to comply with or to secure required permits or approvals for activities regulated by any other applicable codes, rules, statutes, or ordinances. ARTICLE II Definitions Word usage. For the purposes of this chapter, certain terms and words used herein shall be interpreted as follows: A. Words used in the present tense include the future tense; the singular number includes the plural, and the plural number includes the singular; words of masculine gender include feminine gender, and words of feminine gender include masculine gender. 105:

5 105-6 STORMWATER MANAGEMENT B. The words "includes" or "including" shall not limit the term to the specific example but are intended to extend its meaning to all other instances of like kind and character. C. The word "person" includes an individual, firm, association, organization, partnership, trust, company, corporation, or any other similar entity. D. The words "shall" and "must" are mandatory; the words "may" and "should" are permissive. E. The words "used" or "occupied" include the words "intended, designed, maintained, or arranged to be used, occupied, or maintained." Definitions. As used in this chapter, the following terms shall have the meanings indicated: ACCELERATED EROSION The removal of the surface of the land through the combined action of man's activity and the natural processes at a rate greater than would occur because of the natural process alone. ACCESSORY STRUCTURE A structure detached from a principal building located on the same lot and customarily incidental and subordinate to the principal building or use. AGRICULTURAL ACTIVITIES The work of producing crops and raising livestock, including tillage, plowing, disking, harrowing, pasturing, and installation of conservation measures. Construction of new buildings or impervious area is not considered an agricultural activity. ALTERATION As applied to land, a change in topography as a result of the moving of soil and rock from one location or position to another; also, the changing of surface conditions by causing the surface to be more or less impervious; land disturbance. APPLICANT A landowner or developer who has submitted a drainage plan or filed an application for approval to engage in any regulated activities as defined in of this chapter. AS-BUILT DRAWINGS A set of engineering or site drawings that delineates the specific permitted stormwater management facility as actually constructed. BMP (BEST MANAGEMENT PRACTICE) Stormwater structures, facilities, and techniques to maintain or improve the water quality of surface runoff; Pennsylvania Handbook of Best Management Practices for Developing Areas, Spring BUFFER See "riparian buffer." CHANNEL EROSION The widening, deepening, and headward cutting of small channels and waterways due to erosion caused by moderate to large floods. CHESTER CREEK ACT 167 PLAN The plan for managing stormwater runoff in the Chester Creek watershed adopted by Delaware and Chester counties as required by the Act of 105:

6 105-7 CHADDS FORD CODE October 4, 1978, P.L. 864 (Act 167), 3 and known as the "Act 167 Stormwater Management Plan, Chester Creek Watershed." CISTERN An underground reservoir or tank for storing rainwater. COMBINED SEWERS stormwater runoff. A sewerage system that carries both sanitary sewage and CONSERVATION DISTRICT The Delaware and Chester county conservation districts, as appropriate for the individual municipality within the Chester Creek and Brandywine Creek watershed. CULVERT A structure with appurtenant works that carries a stream under or through an embankment or fill. DAM An artificial barrier, together with its appurtenant works, constructed for the purpose of impounding or storing water or another fluid or semifluid, or a refuse bank, fill, or structure for highway, railroad, or other purposes which does or may impound water or another fluid or semifluid. DEED RESTRICTION See "restrictive covenant." DESIGNEE The agent of the Delaware County Planning Department or the Chester County Planning Commission and/or agent of the governing body involved with the administration, review, or enforcement of any provisions of this chapter by contract or memorandum of understanding. DESIGN STORM The magnitude and temporal distribution of precipitation from a storm event measured in probability of occurrence (e.g., a five-year storm) and duration (e.g., 24 hours), used in the design and evaluation of stormwater management systems. DETENTION BASIN An impoundment structure designed to manage stormwater runoff by temporarily storing the runoff and releasing it at a predetermined rate. DETENTION DISTRICT Those subareas in which some type of detention is required to meet the plan requirements and the goals of Act 167. DEVELOPER A person, partnership, association, corporation, or other entity, or any responsible person therein or agent thereof, that undertakes any regulated activity of this chapter. DEVELOPMENT See "land development." DEVELOPMENT SITE proposed. The specific tract of land for which a regulated activity is DISCHARGE EASEMENT The grant of a property right to allow runoff in excess of the previous quantity and/or rate of flow. 3. Editor's Note: See 32 P.S et seq. 105:

7 105-7 STORMWATER MANAGEMENT DOWNSLOPE PROPERTY LINE That portion of the property line of the lot, tract, or parcels of land being developed, located such that all overland or pipe flow from the site would be directed towards it. DRAINAGE CONVEYANCE FACILITY A stormwater management facility designed to transmit stormwater runoff, including streams, channels, swales, pipes, conduits, culverts, storm sewers, etc. DRAINAGE EASEMENT A right granted by a landowner to a grantee allowing the use of private land for stormwater management purposes. DRAINAGE PERMIT A permit issued by the municipality after the drainage plan has been approved. Said permit is issued prior to or with the final municipal approval. EARTH DISTURBANCE Any activity including, but not limited to, construction, mining, timber harvesting, and grubbing which alters, disturbs, and exposes the existing land surface. EASEMENT A right-of-way granted, but not dedicated, for limited use of private land for a public or quasi-public purpose (e.g., utility lines) and within which the owner of the property shall not erect any permanent structures. EPHEMERAL STREAMS Streams that carry only surface runoff and are dry except during precipitation events. The groundwater table is generally located below the bottom of ephemeral streams. EROSION natural forces. The movement of soil particles by the action of water, wind, ice, or other EROSION AND SEDIMENT POLLUTION CONTROL PLAN A plan that is designed to minimize accelerated erosion and sedimentation. Said plan must be submitted to and approved by the Delaware County Conservation District before construction can proceed. EXISTING CONDITIONS The initial condition of a project site prior to the proposed construction. If the initial condition of the site is undeveloped land, the land use shall be considered as "meadow" on "B" soils unless the natural land cover is proven to generate lower curve numbers or Rational "C" value, such as forested lands. FLOOD A general but temporary condition of partial or complete inundation of normally dry land areas from the overflow of streams, rivers, and other waters of this commonwealth. FLOODPLAIN Any land area susceptible to inundation by water from any natural source or delineated by applicable Department of Housing and Urban Development, Federal Insurance Administration, Flood Hazard Boundary Map as being a special flood hazard area. FLOODWAY The channel of the watercourse and those portions of the adjoining floodplains that are reasonably required to carry and discharge the one-hundred-year-frequency flood. Unless otherwise specified, the boundary of the floodway is as indicated on maps and flood insurance studies provided by the Federal Emergency Management Agency (FEMA). In an area where no FEMA maps or studies have defined the boundary of the one-hundred-year-frequency floodway, it is assumed (absent evidence to the 105:

8 105-7 CHADDS FORD CODE contrary) that the floodway extends from the stream to 50 feet from the center line of the stream. FOREST MANAGEMENT/TIMBER OPERATIONS Planning and activities necessary for the management of forest land. These include timber inventory and preparation of forest management plans, silvicultural treatment, cutting budgets, logging road design and construction, timber harvesting, site preparation, and reforestation. FREEBOARD A vertical distance between the elevation of the design high water and the top of a dam, levee, tank, basin, or diversion ridge. The space is required as a safety margin in a pond or basin. GRADE A. A slope, usually of a road, channel, or natural ground, specified in percent and shown on plans as specified herein. B. To finish the surface of a roadbed, top of embankment, or bottom of excavation. GRASSED WATERWAY A natural or constructed waterway, usually broad and shallow, covered with erosion-resistant grasses, used to conduct surface water from cropland. GROUNDWATER RECHARGE supplies. Replenishment of existing natural underground water IMPERVIOUS SURFACE A surface that has been compacted or covered with material to the extent that it is highly resistant to infiltration by water, including, but not limited to, conventional impervious surfaces such as paved streets, roofs, compacted stone, and sidewalks. In addition, the following shall be considered impervious surfaces when used by motor vehicles: graveled areas, paver blocks, bricks, and cobblestone. IMPOUNDMENT A retention or detention basin designed to retain stormwater runoff and release it at a controlled rate. INFILTRATION STRUCTURES A structure designed to direct runoff into the ground (e.g., French drains, seepage pit, and seepage trench). INLET A. A surface connection to a closed drain. B. A structure at the diversion end of a conduit. C. The upstream end of any structure through which water may flow. INTERMITTENT STREAMS Streams which flow only during wet seasons. The groundwater table generally is at or above the bottom of intermittent streams during wet seasons but drops below the stream bottom during dry seasons. Stream flow in intermittent streams is primarily due to precipitation but does have some groundwater contribution during wet seasons. 105:

9 105-7 STORMWATER MANAGEMENT LAND DEVELOPMENT A. The improvement of one lot or two or more contiguous lots, tracts, or parcels of land for any purpose involving: (1) A group of two or more residential or nonresidential buildings, whether proposed initially or cumulatively, or a single nonresidential building on a lot or lots regardless of the number of occupants or tenure; or (2) The division or allocation of land or space, whether initially or cumulatively, between or among two or more existing or prospective occupants by means of, or for the purpose of, streets, common areas, leaseholds, condominiums, building groups, or other features. B. Any subdivision of land. C. Development in accordance with Section 503(1.1) of the Pennsylvania Municipalities Planning Code. 4 LAND/EARTH DISTURBANCE Any activity involving grading, tilling, digging, or filling of ground or stripping of vegetation or any other activity that causes an alteration to the natural condition of the land. MAIN STEM (MAIN CHANNEL) Any stream segment or other runoff conveyance facility used as a reach in the Chester Creek hydrologic model. MANNING EQUATION (MANNING FORMULA) A method for calculation of velocity of flow (e.g., feet per second) and flow rate (e.g., cubic feet per second) in open channels based upon channel shape, roughness, depth of flow, and slope. "Open channels" may include closed conduits so long as the flow is not under pressure. MUNICIPALITY Chadds Ford Township, Delaware County, Pennsylvania. NONPOINT SOURCE POLLUTION Pollution that enters a watery body from diffuse origins in the watershed and does not result from discernible, confined, or discrete conveyances. NRCS Natural Resource Conservation Service [previously the Soil Conservation Service (SCS)]. OPEN CHANNEL A drainage element in which stormwater flows with an open surface. Open channels include, but shall not be limited to, natural and man-made drainageways, swales, streams, ditches, canals, and pipes flowing partly full. OUTFALL Point where water flows from a conduit, stream, or drain. OUTLET Points of water disposal from a stream, river, lake, tidewater, or artificial drain. PARKING LOT STORAGE Involves the use of impervious parking areas as temporary impoundments with controlled release rates during rainstorms. 4. Editor's Note: See 53 P.S :

10 105-7 CHADDS FORD CODE PEAK DISCHARGE event. The maximum rate of stormwater runoff from a specific storm PENN STATE RUNOFF MODEL (CALIBRATED) modeling technique. A computer-based hydrologic PERENNIAL STREAMS Streams that flow year round. Perennial streams derive their flow from both groundwater and runoff, and the groundwater table never drops below the streambed. PIPE A culvert, closed conduit, or similar structure (including appurtenances) that conveys stormwater. PLANNING COMMISSION The Planning Commission of Chadds Ford Township. PMF (PROBABLE MAXIMUM FLOOD) The flood that may be expected from the most severe combination of critical meteorologic and hydrologic conditions that are reasonably possible in any area. The PMF is derived from the probable maximum precipitation (PMP) as determined based on data obtained from the National Oceanographic and Atmospheric Administration (NOAA). RATIONAL FORMULA A rainfall-runoff relation used to estimate peak flow. REDEVELOPMENT Reconstruction of an existing, improved, developed property, as of the date of adoption of this chapter. REGULATED ACTIVITIES Actions or proposed actions that have an impact on stormwater runoff and that are specified in of this chapter. RELEASE RATE The percentage of predevelopment peak rate of runoff from a site or subarea to which the postdevelopment peak rate of runoff must be reduced to protect downstream areas. RESTRICTIVE COVENANT A restriction on the use of land usually set forth in the deed. Restrictive covenants (a.k.a., deed restrictions) usually run with the land and are binding upon subsequent owners of the property. RETENTION BASIN An impoundment in which stormwater is stored and not released during the storm event. Stored water may be released from the basin at some time after the end of the storm. RETURN PERIOD The average interval, in years, within which a storm event of a given magnitude can be expected to recur. For example, the twenty-five-year return period rainfall would be expected to recur on the average once every 25 years. RIPARIAN BUFFER A vegetative strip paralleling the banks of a perennial or intermittent stream or other water body (including wetlands and ponds). The buffer shall contain appropriate native vegetation throughout its width with the exception of a minimum 105:

11 105-7 STORMWATER MANAGEMENT five-foot-wide strip of land maintained in meadow grass or forbs at its outer boundary. See also Appendix C, Riparian Buffer Technical Reference Guide. 5 RISER A vertical pipe extending from the bottom of a pond that is used to control the discharge rate from the pond for a specified design storm. ROOFTOP DETENTION Temporary ponding and gradual release of stormwater falling directly onto flat roof surfaces by incorporating controlled-flow roof drains into building designs. RUNOFF Any part of precipitation that flows over the land surface. SEDIMENT BASIN A barrier, dam, or retention or detention basin located and designed to retain rock, sand, gravel, silt, or other material transported by water. SEDIMENT POLLUTION The placement, discharge, or any other introduction of sediment into the waters of the commonwealth occurring from the failure to design, construct, implement, or maintain control measures and control facilities in accordance with the requirements of this chapter. SEDIMENTATION movement of water. The process by which matter is accumulated or deposited by the SEEPAGE PIT/SEEPAGE TRENCH An area of excavated earth filled with loose stone or similar coarse material into which surface water is directed for infiltration into the ground. SHEET FLOW Runoff that flows over the ground surface as a thin, even layer, not concentrated in a channel. SOIL-COVER COMPLEX METHOD A method of runoff computation developed by the NRCS that is based on relating soil type and land use/cover to a runoff parameter called "curve number (CN)." SOIL GROUP, HYDROLOGIC A classification of soils by SCS 6 into four runoff potential groups. The groups range from A soils, which are very permeable and produce little runoff, to D soils, which are not very permeable and produce much more runoff. SPILLWAY A depression in the embankment of a pond or basin that is used to pass the peak discharge which is greater than the maximum design storm controlled by the pond. STORAGE INDICATION METHOD A reservoir routing procedure based on solution of the continuity equation (inflow minus outflow equals the change in storage) with outflow defined as a function of storage volume and depth. STORM FREQUENCY The number of times that a given storm event occurs or is exceeded on the average in a stated period of years. See "return period." 5. Editor's Note: Appendix C is included at the end of this chapter. 6. Editor's Note: Now the Natural Resource Conservation Service (NRCS). 105:

12 105-7 CHADDS FORD CODE STORM SEWER A system of pipes and/or open channels that conveys intercepted runoff and stormwater from other sources but excludes domestic sewage and industrial wastes. STORMWATER The total amount of precipitation reaching the ground surface. STORMWATER MANAGEMENT FACILITY Any structure, natural or man-made, that, due to its condition, design, or construction, conveys, stores, or otherwise affects stormwater runoff. Typical stormwater management facilities include, but are not limited to, detention and retention basins, open channels, storm sewers, pipes, and infiltration structures. STORMWATER MANAGEMENT PLAN The documentation of the stormwater management system, if any, to be used for a given development site, the contents of which are established in STORMWATER MANAGEMENT SITE PLAN The plan prepared by the applicant or his representative indicating how stormwater runoff will be managed at the particular site of interest according to this chapter. STREAM ENCLOSURE A bridge, culvert, or other structure in excess of 100 feet in length upstream to downstream which encloses a regulated water of this commonwealth. SUBAREA The smallest drainage unit of a watershed for which stormwater management criteria have been established in the stormwater management plan. SUBDIVISION The division or redivision of a lot, tract, or parcel of land by any means into two or more lots, tracts, parcels, or other divisions of land including changes in existing lot lines for the purpose, whether immediate or future, of lease, transfer of ownership, or building or lot development; provided, however, that the subdivision by lease of land for agricultural purposes into parcels of more than 10 acres not involving any new street or easement of access or any residential dwellings shall be exempt. SWALE A low-lying stretch of land that gathers or carries surface water runoff. TIMBER OPERATIONS See "forest management." TIME OF CONCENTRATION (TC) The time for surface runoff to travel from the hydraulically most distant point of the watershed to a point of interest within the watershed. This time is the combined total of overland flow time and flow time in pipes or channels, if any. TR-20 The computer-based hydrologic modeling technique adapted to the Chester Creek watershed for the Act 167 plan. The model has been "calibrated" to reflect actual recorded flow values by adjusting key model input parameters. TR-55 A method for determining runoff volumes and rates developed by NRCS. WATERCOURSE A channel or conveyance of surface water having defined bed and banks, whether natural or artificial, with perennial or intermittent flow. WATERS OF THE COMMONWEALTH Any and all rivers, streams, creeks, rivulets, ditches, watercourses, storm sewers, lakes, dammed water, wetlands, ponds, springs, and all 105:

13 105-7 STORMWATER MANAGEMENT other bodies or channels of conveyance of surface and underground water, or parts thereof, whether natural or artificial, within or on the boundaries of this commonwealth. WETLAND Those areas that are inundated or saturated by surface water or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions, including swamps, marshes, bogs, and similar areas. ARTICLE III Stormwater Management Plan Requirements General requirements. For any of the activities regulated by this chapter, the final approval of subdivision and/or land development plans, the issuance of any building or occupancy permit, or the commencement of any land disturbance activity may not proceed until the applicant or his/her agent has received written approval of a stormwater management plan from the municipality Exemptions. A. Stormwater quantity control exemption. (1) Any regulated activity that meets the following exemption criterion shall not be required to submit a stormwater management plan implementing the stormwater quantity controls of this chapter. This criterion shall apply to the total development even if the development is to take place in phases. The date of the municipal ordinance adoption shall be the starting point from which to consider tracts as "parent tracts" in which future subdivisions and respective impervious area computations shall be cumulatively considered. Exemption shall not relieve the applicant from implementing such measures as are necessary to protect health, safety, and property. (2) Stormwater management exemption criterion: (a) (b) (c) (d) (e) The use of the land for gardening for home consumption. Normal agricultural operations. Any land grading activity where the proposed increase in impervious coverage is less than 750 square feet. Any land grading activity where the total area disturbed at one time does not exceed 4,000 square feet. Any land grading activity where the grade level is not changed to an extent which alters the direction or increases the rate of stormwater runoff as determined by the Township. B. Applicants whose activities are exempted under Subsection A above shall still be required to meet the stormwater management quality controls of this chapter. This may 105:

14 105-9 CHADDS FORD CODE be achieved by implementing one or more of the following minimum best management practices: (1) Provide infiltration capacity for the equivalent of one inch of runoff from all new impervious surfaces. The infiltration volume does not have to be provided in one location. However, if site conditions preclude capture of runoff from portions of the impervious area, the infiltration volume for the remaining area should be increased an equivalent amount to offset the loss. In no case should the portion of the new impervious area flowing to an infiltration facility be less than 70% of the total new impervious area. (2) If site conditions preclude use of infiltration facilities (e.g., high groundwater table or extensive rock conditions), provide an extended detention facility that will detain the equivalent of one inch of runoff from all new impervious areas for at least 24 hours. (3) Provide buffer areas on the downstream side of any new impervious surfaces (e.g., sidewalks, roadways, parking lots) where the runoff discharges in a sheet flow manner. The buffer areas should be at least 20 feet wide and can be a mix of grass, shrubs, and trees. If buffer areas cannot be provided for the entire length of the impervious surfaces, consider installing a bioretention system and diverting surface runoff from the impervious surfaces to the facility using grass swales. (4) If none of the above options are feasible due to site constraints, the applicant must provide stormwater detention that meets the release rate criteria for the site location or else obtain approval from the Municipal Engineer to implement other BMPs that will provide water quality benefits of an equivalent level. C. New federal regulations approved October 1999 require operators of small municipal separate storm sewer systems (MS4s) to obtain NPDES Phase II permits from DEP by March ("NPDES II" is an acronym for the National Pollutant Discharge Elimination System Phase II Stormwater Permitting Regulations.) This program affects all municipalities in "urbanized areas" of the state. This definition applies to all Chester Creek watershed municipalities. Therefore, all municipalities within the Chester Creek watershed will be subject to the NPDES Phase II requirements, mandated by the Federal Clean Water Act as administered by DEP Plan submission. For all activities regulated by this chapter, the steps below shall be followed for submission. For any activities that require a DEP joint permit application and are regulated under Chapter 105 (Dam Safety and Waterway Management) or Chapter 106 (Floodplain Management) of DEP's Rules and Regulations, require a PennDOT highway occupancy permit, or require any other permit under applicable state or federal regulations, the permit(s) shall be part of the plan. A. Five copies of the drainage plan and associated plan review application shall be submitted by the applicant as part of the Act 247 preliminary plan submission for the regulated activity. Distribution of the drainage plan will be as follows: 105:

15 STORMWATER MANAGEMENT (1) Two copies to the municipality accompanied by the requisite municipal review fee. (2) One copy to the Municipal Engineer. (3) One copy to the County Planning Department. (4) One copy to the County Conservation District Plan contents. The drainage plan shall consist of all applicable calculations, maps, and plans. A note on the maps shall refer to the associated computations and erosion and sedimentation control plan by title and date. The cover sheet of the computations and erosion and sedimentation control plan shall refer to the associated maps by title and date. All drainage plan materials shall be submitted to the municipality in a format that is clear, concise, legible, neat, and well organized; otherwise, the drainage plan shall be disapproved and returned to the applicant. The following items shall be included: A. General. (1) General description of project. (2) General description of permanent stormwater management techniques, including construction specifications of the materials to be used for stormwater management facilities. (3) Complete hydrologic, hydraulic, and structural computations for all stormwater management facilities. (4) All storm drains and drainage facilities such as pipes, gutters, inlets, catch basins, culverts and other proposed structures necessary for the collection, retention and conveyance of stormwater runoff shall be delineated, depicted and otherwise noted at the time of stormwater management plan submission as provided in this chapter. (5) The stormwater management plan shall take into account and provide for upstream areas within the entire watershed in computing discharge quantities, sizing of pipes, inlets and other structures. The runoff from any proposed development shall be subject to evaluation, which includes the anticipated runoff from other existing or proposed developments within the same watershed. B. Plans of the project area shall be submitted on sheets that do not exceed 30 inches by 42 inches and shall be prepared in a form that meets the requirements for recording at the offices of the Recorder of Deeds of Delaware County. The contents of the plans shall include, but not be limited to: (1) The location of the project relative to highways, municipalities, or other identifiable landmarks. (2) Existing contours at intervals of two feet. 105:

16 CHADDS FORD CODE (3) Existing streams, lakes, ponds, or other bodies of water and wetlands within the project area. (4) Other physical features including flood hazard boundaries, streams, existing drainage courses, areas of natural vegetation to be preserved, and the total extent of the upstream area draining through the site. (5) The locations of all existing and proposed structures and utilities within 50 feet of property lines. (6) An overlay showing soil names and boundaries. (7) Proposed changes to the land surface and vegetative cover, including the type and amount of impervious area that would be added. (8) Proposed structures, roads, paved areas, and buildings. (9) Final contours at intervals of two feet. In areas of steep slopes (greater than 15%), five-foot contour intervals may be used. (10) The name of the development, the name and address of the owner of the property, and the name of the individual or firm preparing the plan. (11) The date of the plan, including revisions. (12) A graphic and written scale at a minimum of one inch equals no more than 50 feet. (13) A north arrow. (14) The total tract boundary and size with distances marked to the nearest foot and bearings to the nearest degree. (15) Existing and proposed land use(s). (16) Vertical profiles of all proposed open channels and storm sewers including hydraulic capacity for both. (17) Overland drainage paths of proposed swales or channels to convey water. (18) A note on the plan indicating the location, access, and responsibility for maintenance of stormwater management facilities. (19) A statement, signed by the landowner, acknowledging the stormwater management system to be a permanent fixture that can be altered or removed only after approval of a revised plan by the municipality. (20) The following signature block for the design engineer: "(Design Engineer), on this date (date of signature), has reviewed and hereby certifies that the stormwater management plan meets all design standards and criteria of the Chester Creek Stormwater Management Plan and this chapter." 105:

17 STORMWATER MANAGEMENT (21) The capacity of each inlet shall be indicated on the stormwater management plan. (22) For the purpose of this section, streams and intermittent streams are defined as those watercourses depicted on the Chadds Ford Township Zoning Map, the USGS maps of the area, and/or determined as such pursuant to an on-site survey by the Township or its representative. (23) If the applicant is proposing a retention/detention basin, the following notes shall be included on the plans: (a) (b) (c) Any/all stormwater conveyance system(s) and detention facilities shown on these plans are a basic and perpetual part of the stormwater management system for this Township, and, as such, are to be protected, maintained and preserved in accordance with the approved final plans. The Township and/or its agents may preserve the right and privilege to enter upon such lands from time to time for the purpose of inspection of said stormwater management system in order to determine that the structural design and integrity are being maintained. In the event that the party or parties responsible for the maintenance of the stormwater management facilities in the development fail to properly maintain said facilities, Chadds Ford Township may, but shall not be obligated to, provide said parties with 30 days' notice of the Township's intention to perform said maintenance or repair. In the event that said parties do not perform or commence to perform said maintenance or repair within the thirty-day notice period, Chadds Ford Township may, but shall not be obligated to, perform said maintenance or repair and charge the cost thereof, including any fees of the Township professionals (including reasonable attorney's fees), to the property owner, and Chadds Ford Township may file a lien against the property until such amounts are fully reimbursed to Chadds Ford Township. The developer and/or contractor shall provide a schedule of work and notify the Township Engineer no less than 48 hours prior to commencing any work on any site improvements. The first item in the sequence of construction shall note that a site meeting shall be conducted and introduce the following parties: [1] Developer. [2] Design engineers. [3] All contractors. [4] Township engineers. [5] Code Enforcement Officer. [6] Delaware County Conservation District. (d) The developer agrees to indemnify and hold Chadds Ford Township harmless for any stormwater directed off-site. 105:

18 CHADDS FORD CODE (e) (f) (g) Nothing shall be permitted to be set on, placed or planted within the area of any utility or stormwater easement except lawns or suitable low ground cover. All contractors working on this project shall be responsible for insuring that all construction activities related to this project are performed in accordance with all OSHA (Occupational Safety and Health Administration) standards and requirements. The developer and/or the contractor shall ensure that all necessary permits and approvals have been obtained and provide copies of such to Chadds Ford Township prior to commencement of any site construction activities. C. Supplemental information. (1) A written description of the following information shall be submitted: (a) (b) (c) (d) The overall stormwater management concept for the project. Stormwater runoff computations as specified in this chapter. Stormwater management techniques to be applied both during and after development. Expected project time schedule. (2) A soil erosion and sedimentation control plan, where applicable, including all reviews and approvals, as required by DEP. (3) The effect of the project (in terms of runoff volumes and peak flows) on adjacent properties and on any existing municipal stormwater collection system that may receive runoff from the project site. (4) The Board of Supervisors may require that a landowner or developer provide reasonable corrective measures to alleviate an existing off-site drainage problem, which may be affected by the proposed subdivision and/or land development. It shall be the responsibility of the landowner or developer to obtain all drainage easements on, over, or through other properties, and the Township, its agents, workmen, servants and employees shall be indemnified and held harmless from any liability. (5) Any subdivision and/or land development within a flood control district shall comply with all of the provisions of the Chadds Ford Township flood control district as provided in Chapter 135, Zoning, and the rules and regulations of the Pennsylvania Department of Environmental Protection. (6) All areas containing lakes, ponds, wetlands and watercourses shall be considered to be reserved for permanent open space. Any alteration, development, filling, piping or diverting of such water resources shall be in strict compliance with the provisions of Chapter 135, Zoning, especially those pertaining to the flood control district, and all prevailing rules and regulations of the state. 105:

19 STORMWATER MANAGEMENT (7) All storm sewer easements through undedicated land shall be a minimum of 20 feet in width. (8) Where a site is traversed by a watercourse, a drainage easement or right-of-way conforming substantially with the line of such watercourse and of such width as will be adequate to preserve natural drainage and provide sufficient width for maintenance shall be created, as determined by the Township. D. Stormwater management facilities. (1) All stormwater management facilities must be located on a plan and described in detail. (2) When groundwater recharge methods such as seepage pits, beds, or trenches are used, the locations of existing and proposed septic tank infiltration areas and wells must be shown. (3) All calculations, assumptions, and criteria used in the design of the stormwater management facilities must be shown Plan review. A. The Municipal Engineer shall review the stormwater management plan for consistency with the adopted Chester Creek Stormwater Management Plan requirements and those other applicable requirements of this chapter. The municipality shall require receipt of a complete plan, as specified in this chapter. The Municipal Engineer shall review the stormwater management plan for any submission or land development against the municipal subdivision and land development ordinance provisions not superseded by this chapter. 7 B. The conservation district, in accordance with established criteria and procedures, shall review the stormwater management plan for consistency with stormwater management and erosion and sediment pollution control requirements and provide comments to the municipality. Such comments shall be considered by the municipality prior to final approval of the stormwater management plan. C. For activities regulated by this chapter, the Municipal Engineer shall notify the municipality in writing as to whether the stormwater management plan is consistent with this chapter. Should the stormwater management plan be determined to be consistent with this chapter, the Municipal Engineer will forward an approval letter to the applicant with a copy to the Municipal Secretary. D. Should the stormwater management plan be determined to be inconsistent with this chapter, the Municipal Engineer will forward a disapproval letter to the applicant with a copy to the Municipal Secretary citing the reason(s) for the disapproval. Any disapproved stormwater management plans may be revised by the applicant and resubmitted consistent with this chapter. 7. Editor's Note: See Ch. 110, Subdivision and Land Development. 105:

20 CHADDS FORD CODE E. For regulated activities specified in of this chapter, the Municipal Engineer shall notify the Township Code Enforcement Officer in writing, within a time frame consistent with the Act 167 Plan, as to whether the stormwater management plan is consistent with the chapter requirements and forward a copy of the approval/disapproval letter to the applicant. Any disapproved stormwater management plan may be revised by the applicant and resubmitted consistent with this chapter. F. For regulated activities requiring a DEP joint permit application, the Municipal Engineer shall notify DEP as to whether the stormwater management plan is consistent with this chapter and forward a copy of the review letter to the municipality and the applicant. DEP may consider the Municipal Engineer's review comments in determining whether to issue a permit. G. The municipality shall not approve any subdivision or land development for regulated activities specified in of this chapter if the stormwater management plan has been found to be inconsistent with this chapter, as determined by the Municipal Engineer. All required permits from DEP must be obtained prior to approval. H. The Municipal Building Permit Officer shall not issue a building permit for any regulated activity specified in of this chapter if the stormwater management plan has been found to be inconsistent with this chapter, as determined by the Municipal Engineer, or without considering the comments of the Municipal Engineer. All required permits from DEP must be obtained prior to issuance of a building permit. I. The applicant shall be responsible for completing as-built drawings of all stormwater management facilities included in the approved stormwater management plan. The as-built drawing and an explanation of any discrepancies with the design plans shall be submitted to the Municipal Engineer for final approval. J. The municipality's approval of a stormwater management plan shall be valid for a period not to exceed five years. This five-year period shall commence on the date that the municipality signs the approved stormwater management plan. If stormwater management facilities included in the approved stormwater management plan have not been constructed, or if as-built drawings of these facilities have not been approved within this five-year time period, then the municipality may consider the stormwater management plan disapproved and may revoke any and all permits. Stormwater management plans that are considered disapproved by the municipality shall be resubmitted in accordance with of this chapter Modification of plans. A. A modification to a submitted stormwater management plan for a development site that involves a change in stormwater management facilities or techniques, or that involves the relocation or redesign of stormwater management facilities, or that is necessary because soil or other conditions are not as stated on the stormwater management plan as determined by the Municipal Engineer, shall require a resubmission of the modified stormwater management plan consistent with of this chapter and be subject to review as specified in of this chapter. 105:

21 STORMWATER MANAGEMENT B. A modification to an already approved or disapproved drainage plan shall be submitted to the municipality, accompanied by the applicable review fee. A modification to a drainage stormwater management plan for which a formal action has not been taken by the municipality shall be submitted to the municipality, accompanied by the applicable municipal review fee Resubmission of disapproved drainage stormwater management plans. A disapproved drainage stormwater management plan may be resubmitted, with the revisions addressing the Municipal Engineer's concerns documented in writing, to the Municipal Engineer in accordance with of this chapter and be subject to review as specified in of this chapter. The applicable municipal review fee must accompany a resubmission of a disapproved drainage stormwater management plan. ARTICLE IV Stormwater Management Provisions General procedures for water quality and quantity control. A. All regulated activities in the Township which do not fall under the exemption criterion shown in shall submit a drainage stormwater management plan consistent with this chapter to the municipality for review. This criterion shall apply to the total proposed development even if development is to take place in stages. Impervious cover shall include, but not be limited to, any roof, parking, or driveway areas and any new streets and sidewalks. Any areas designed to initially be gravel or crushed stone shall be assumed to be impervious. B. Drainage stormwater management plans shall be prepared in accordance with the provisions contained in this article. The process for implementing these provisions is illustrated in Figure 4-1, Water Quality and Quantity Control Drainage Plan Preparation Procedure. 8 C. This chapter requires water quality and water quantity controls as illustrated on the flow chart shown in Figure 4-1 and detailed in The flow chart illustrates a three-step hierarchical process: Step 1, Infiltration; Step 2, Extended detention; and Step 3, Implementation of additional design controls. Applicants must evaluate the outcome of each step before proceeding to the next. In addition, riparian buffers are required where applicable, in accordance with A(2). D. Applicants are highly encouraged to meet the postdevelopment peak discharge control criteria indicated in , and through use of BMPs and innovative site designs that minimize the amount of new impervious surface. E. Any water originating from non-natural sources, such as swimming pools, air-conditioning units, sump pumps, roof drains, or other similar flow, shall be properly discharged into natural watercourses or storm drains. 8. Editor's Note: Figure 4-1 is included at the end of this chapter. 105:

22 CHADDS FORD CODE Stormwater management districts. A. The Chester Creek watershed is divided into districts that represent three levels of stormwater management. The boundaries of the stormwater management districts are shown on an official release rate map, included as part of the Chester Creek Stormwater Management Plan (see Plate 6, Release Rate Map). A copy of the official release rate map at a reduced scale is included as Plate 1 in Appendix A of this chapter. 9 This map is for reference only. The exact location of the stormwater management district boundaries as they apply to a given development site must be determined by mapping the boundaries using the two-foot topographic contours (or the most accurate data required) provided as part of the drainage stormwater management plan. B. All other areas of the municipality shall use the Brandywine Creek watershed stormwater management district implementation provisions Chester Creek watershed stormwater management district implementation provisions (performance standards). A. General. Postdevelopment rates of runoff from any regulated activity shall not exceed the peak release rates of runoff prior to development for the design storms specified on the official stormwater management release rate map, Appendix A, 10 and of the chapter, whichever applies. B. Standards for managing runoff. (1) Standards for managing runoff for new development from each subarea in the Chester Creek watershed for the two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year design storms are shown in Table 1. Development sites located in each of the districts must control postdevelopment peak runoff rates to the specified percentage of predevelopment peak runoff rates for the design storms as shown in the table. Table 1 Control Criteria for Stormwater Management Districts District Control Criteria 100% Postdevelopment peak discharge for all design storms must be no greater than predevelopment peak discharges 75% Postdevelopment peak discharge for all design storms must be no greater than 75% of the predevelopment peak discharges 50% Postdevelopment peak discharge for all design storms must be no greater than 50% of the predevelopment peak discharges 9. Editor's Note: Appendix A is included at the end of this chapter. 10. Editor's Note: Appendix A is included at the end of this chapter. 105:

23 STORMWATER MANAGEMENT Source: Gannett Fleming, 2001 (2) All other areas of the municipality shall use the Brandywine Creek watershed stormwater management district implementation provisions. C. Redevelopment projects shall meet peak discharge requirements based on the adjusted runoff control number (RCN) or "C" value illustrated by Figure B-3 in Appendix B. 11 D. Sites located in more than one district. For a proposed development site located within two or more release category subareas, the peak discharge rate from any subarea shall be the predevelopment peak discharge for each subarea multiplied by the applicable release rate. The calculated peak discharges shall apply regardless of whether the grading plan changes the drainage area by subarea. E. Off-site areas. Off-site areas that drain through a proposed development site are not subject to release rate criteria when determining allowable peak runoff rates. However, on-site drainage facilities shall be designed to safely convey off-site flows through the development site. F. Site areas. Where the site area to be impacted by a proposed development activity differs significantly from the total site area, as determined by the Municipal Engineer, only the proposed development area and areas contributory to the proposed stormwater management facilities shall be subject to the release rate criteria Brandywine Creek watershed stormwater management district implementation provisions (performance standards). After installation of impervious cover, peak discharge from the site shall not exceed the before-construction peak discharge rate from a two-year, twenty-four-hour storm to all storms up to a ten-year, twenty-four-hour storm. Peak discharges for any storms of greater than ten-year frequency, up to and including a one-hundred-year storm, shall not exceed the preconstruction rates of discharges from the site before development of such storms, including: A. A twenty-five-year, twenty-four-hour storm; B. A fifty-year, twenty-four-hour storm; and C. A one-hundred-year, twenty-four-hour storm Water quality requirements for all areas of the Township. A. In addition to the performance standards and design criteria requirements of , and and through of this chapter, the applicant shall comply with the following water quality requirements unless otherwise exempted by provisions of this chapter: 11. Editor's Note: Appendix B is included at the end of this chapter. 105:

24 CHADDS FORD CODE (1) The applicant shall first provide infiltration facilities in areas where soils are suitable for infiltration and shall direct the runoff from impervious surfaces into those infiltration facilities. The volume of storage to be provided shall be no less than the net increase in runoff from the two-year storm event, or one inch of runoff from the total area draining to the infiltration facility, whichever is greater. (2) If a perennial or intermittent stream passes through the site, the applicant shall create a riparian buffer extending a minimum of 50 feet measured from the center line of the stream. The buffer area shall be maintained with appropriate native vegetation (see list of technical references in Appendix C of this chapter 12 ). If the applicable rear or side yard setback is less than 50 feet, the buffer width may be reduced to 25% of the setback to a minimum of 10 feet. If an existing buffer is legally prescribed (e.g., deed covenant, easement, etc.) and it exceeds the requirement of this chapter, the existing buffer shall be maintained. (3) Detain the two-year, twenty-four-hour design storm runoff based on using the SCS Type II distribution. Provisions shall be made so that the detained runoff takes a minimum of 24 hours to drain from the facility from a point where the maximum volume of water is captured (i.e., the maximum water surface elevation is achieved in the facility). Release of water can begin at the start of the storm (i.e., the invert of the water quality orifice is at the invert of the facility). The design of the facility shall consider and minimize the chances of clogging and sedimentation potential. The applicant may also utilize infiltration facilities in lieu of extended detention. The volume of infiltration provided for the contributing area may be deducted from the volume requirement for extended detention. B. The applicant shall submit designs for water quality facilities to the Municipal Engineer for review and approval. Such designs may achieve the water quality objectives through a combination of BMPs. C. In selecting the appropriate BMPs or combinations thereof, the applicant shall consider the following: (1) Total contributing area. (2) Permeability and infiltration rate of the site soils. (3) Slope and depth to bedrock. (4) Seasonal high water table. (5) Proximity to building foundations and well heads. (6) Erodibility of soils. (7) Land availability and configuration of the topography. (8) Consistency with approved watershed and stormwater management plans or regulations. 12. Editor's Note: Appendix C is included at the end of this chapter. 105:

25 STORMWATER MANAGEMENT D. The following additional factors should be considered when evaluating the suitability of BMPs used to control water quality at a given development site: (1) Peak discharge and required volume control. (2) Streambank erosion. (3) Efficiency of the BMPs to mitigate potential water quality problems. (4) The volume of runoff that will be effectively treated. (5) The nature of the pollutant being removed. (6) Maintenance requirements. (7) Creation/protection of aquatic and wildlife habitat. (8) Recreational value. (9) Enhancement of aesthetic and property value Calculation methodology. A. Any stormwater runoff calculations involving drainage areas greater than 200 acres, including on- and off-site areas, shall use a generally accepted calculation technique that is based on the NRCS soil-cover complex method. Table 2 summarizes acceptable computation methods. It is assumed that all methods will be selected by the design professional based on the individual limitations and suitability of each method for a particular site. Table 2 Acceptable Computation Methodologies for Stormwater Management Plans Method Developed Method by Applicability TR-20 or commercial USDA NRCS When use of full model is desirable package based on TR-20 or necessary TR-55 or commercial USDA NRCS Applicable for plans within the package based on TR-55 model's limitations HEC-HMS U.S. Army Corps of When use of full model is desirable Engineers or necessary PSRM Penn State University. When use of full model is desirable or necessary Rational Method or Emil Kuiching (1889) For sites with a total contributing commercial package based drainage area of less than five on Rational Method 1 acres Other methods Various As approved by the Municipal Engineer 105:

26 CHADDS FORD CODE NOTE: 1 Use of the Rational Method to estimate peak discharges from drainage areas that contain more than five acres must be approved by the Municipal Engineer. Source: Gannett Fleming, 2001 B. All calculations consistent with this chapter using the soil-cover complex method shall use the appropriate design rainfall depths for the various return period storms presented in Table B-1 in Appendix B of this chapter. 13 If a hydrologic computer model such as PSRM or HEC-1 is used for stormwater runoff calculations, then the duration of rainfall shall be 24 hours. The NRCS "S" curve shown in Figure B-1, Appendix B, of this chapter shall be used for the rainfall distribution. C. For the purposes of predevelopment flow rate determination, undeveloped land shall be considered as "meadow" good condition, type "B" soils (RCN = 58, Rational "C" = 0.12) unless the natural ground cover generates a lower curve number or Rational "C" value (i.e., forest). If a proposed development meets the definition of redevelopment as defined in Article II of this chapter, the applicant may adjust the predevelopment RCN or "C" value based on the curves presented in Figure B-3. D. All calculations using the Rational Method shall use rainfall intensities consistent with appropriate times of concentration for overland flow and return periods from the design storm curves from the Pennsylvania Department of Transportation Design Rainfall Curves (1986) (Figure B-2). Times of concentration for overland flow shall be calculated using the methodology presented in Chapter 3 of Urban Hydrology for Small Watersheds, NRCS, TR-55 (as amended or replaced from time to time by NRCS). Times of concentration for channel and pipe flow shall be computed using Manning's Equation. E. RCNs for both existing and proposed conditions to be used in the soil-cover complex method shall be obtained from Table B-2 in Appendix B of this chapter. F. Runoff coefficients (C) for both existing and proposed conditions for use in the Rational Method shall be obtained from Table B-3 in Appendix B of this chapter. G. Runoff characteristics of off-site areas that drain through a proposed development shall be based on actual existing conditions, not RCN = 58 or C = 0.12, and shall be assumed to not have any controls implemented on future development (i.e., no release rate restrictions). H. Where uniform flow is anticipated, the Manning Equation shall be used for hydraulic computations and to determine the capacity of open channels, pipes, and storm sewers. Values for Manning's roughness coefficient (n) shall be consistent with Table B-4 in Appendix B of the chapter. I. Outlet structures for stormwater management facilities shall be designed to meet the performance standards of this chapter using any generally accepted hydraulic analysis technique or method. Acceptable methods are presented in Handbook of Hydraulics, by King and Brater (McGraw Hill). In addition, application of computer programs such as 13. Editor's Note: Appendix B is included at the end of this chapter. 105:

27 STORMWATER MANAGEMENT HY-8 (Federal Highway Administration) or FlowMaster (Haestad Methods) will also be accepted. J. The design of any stormwater detention facilities intended to meet the performance standards of this chapter shall be verified by routing the design storm hydrograph through these facilities using the Storage-Indication Method. For drainage areas greater than 20 acres in size, the design storm hydrograph shall be computed using a calculation method that produces a full hydrograph. The municipality may approve the use of any generally accepted full hydrograph approximation technique that uses a total runoff volume that is consistent with the volume from a method that produces a full hydrograph. K. The municipality has the authority to require that computed existing runoff rates be reconciled with field observations and conditions. If the designer can substantiate through actual physical calibration that more appropriate runoff and time-of-concentration values should be utilized at a particular site, then appropriate variations may be made upon review and recommendation of the Municipal Engineer. Calibration shall require detailed gauge and rainfall data for the particular site in question Design criteria for stormwater management facilities. A. Any stormwater management facility (i.e., detention basin) designed to store runoff and requiring a berm or earthen embankment required or regulated by this chapter shall be designed to provide an emergency spillway to handle flow up to and including the one-hundred-year postdevelopment conditions. The height of the embankment must be set so as to provide a minimum one 2.0 feet of freeboard above the maximum pool elevation computed when the facility functions for the one-hundred-year postdevelopment inflow. Should any stormwater management facility require a dam safety permit under DEP Chapter 105, the facility shall be designed in accordance with Chapter 105 and meet the regulations of Chapter 105 concerning dam safety which may be required to pass storms larger than the one-hundred-year event. B. Any facilities that constitute water obstructions (e.g., culverts, bridges, outfalls, or stream enclosures) and any work involving wetlands as directed in DEP Chapter 105 regulations (as amended or replaced from time to time by DEP) shall be designed in accordance with Chapter 105 and will require a permit from DEP. Any other drainage conveyance facility that does not fall under Chapter 105 regulations shall be designed to convey, without damage to the drainage structure or roadway, runoff from a minimum twenty-five-year design storm. Municipalities may require design based on a larger storm event. Open channels shall be designed with a minimum of one foot of freeboard. Any facility that constitutes a dam as defined in DEP Chapter 105 regulations may require a permit under dam safety regulations. Any facility located within a PennDOT right-of-way must meet PennDOT minimum design standards and permit submission requirements. If the primary drainage facilities do not have capacity for future flows, then a safe drainage path must be provided to convey up to the one-hundred-year design storm (without impacting structures). 105:

28 CHADDS FORD CODE C. Storm sewers must be able to convey postdevelopment runoff from a minimum twenty-five-year design storm without surcharging inlets. D. Groundwater recharge. In general, all runoff control measures shall be designed to encourage groundwater recharge and shall be permitted only if suitable surface conditions are present. Soils testing and certification by a registered professional engineer, geologist, soils scientist, or the like shall be required before any groundwater recharge system will be allowed. E. Adequate erosion protection shall be provided along all open channels and at all points of discharge. F. The design of all stormwater management facilities shall incorporate sound engineering principles and practices. The municipality shall reserve the right to disapprove any design that would result in the occurrence or continuation of an adverse hydrologic or hydraulic condition within the watershed. G. Stormwater drainage systems shall be provided in order to permit unimpeded flow along natural watercourses, except as modified by stormwater management facilities or open channels consistent with this chapter. H. The existing points of concentrated drainage that discharge onto adjacent property shall not be altered without permission of the adjacent property owner(s) and shall be subject to any applicable discharge criteria specified in this chapter. I. Areas of existing diffused drainage discharge shall be subject to any applicable discharge criteria in the general direction of existing discharge, whether proposed to be concentrated or maintained as diffused drainage areas, except as otherwise provided by this chapter. If diffused flow is proposed to be concentrated and discharged onto adjacent property, the applicant must document to the municipality in accordance with that adequate downstream conveyance exists to safely transport the concentrated discharge, or the applicant must obtain drainage easements from affected downstream property owners and provide the facilities to safely convey the flow. J. Downstream hydraulic capacity analysis. Any downstream capacity hydraulic analysis conducted in accordance with this chapter shall use the following criteria for determining adequacy for accepting increased peak flow rates: (1) Natural or man-made channels or swales must be able to convey the increased runoff associated with a two-year return period event within their banks at velocities consistent with protection of the channels from erosion. Acceptable velocities shall be based upon criteria included in the DEP Erosion and Sediment Pollution Control Program Manual. (2) Natural or man-made channels or swales must be able to convey the increased twenty-five-year return period runoff without creating any hazard to persons or property. (3) Culverts, bridges, storm sewers, or any other facilities which must pass or convey flows from the tributary area must be designed in accordance with DEP Chapter 105:

29 STORMWATER MANAGEMENT regulations (if applicable) and, at a minimum, pass the increased twenty-five-year return period runoff. K. Where a development site is traversed by watercourses, riparian buffers shall be provided conforming to the line of such watercourses. The width of the buffers shall be determined as set forth in A(2). Excavating, placing of fill, building structures, or making any alterations that may adversely affect the flow of stormwater within any portion of the riparian buffer shall be prohibited unless the proposed work is associated with a regulated wetlands mitigation program. The buffer must be defined through a deed covenant. L. When it can be shown that, due to topographic conditions, natural drainageways on the site cannot adequately provide for drainage, open channels may be constructed conforming substantially to the line and grade of such natural drainageways. Work within natural drainageways shall be subject to approval by DEP through the joint permit application process, or, where deemed appropriate by DEP, through the general permit process. M. Any stormwater management facilities regulated by this chapter that would be located in or adjacent to waters of the commonwealth or wetlands shall be subject to approval by DEP through the joint permit application process, or, where deemed appropriate by DEP, the general permit process. When there is a question as to whether wetlands may be involved, it is the responsibility of the applicant or his agent to show that the land in question cannot be classified as wetlands; otherwise, approval to work in the area must be obtained from DEP. N. Any stormwater management facilities regulated by this chapter that would be located on state highway rights-of-way shall be subject to approval by PennDOT. O. Minimization of impervious surfaces and infiltration of runoff through seepage beds, infiltration trenches, etc., are required, where soil conditions permit, to reduce the size or eliminate the need for detention facilities. P. In order to promote overland flow and infiltration/percolation of stormwater, roof drains must discharge into an accepted BMP providing infiltration and filtering of the stormwater. Q. Detention/retention basins. (1) Basins shall be designed to detain the quantity of water resulting from a one-hundred-year, twenty-four-hour storm (7.2 inches of rainfall) under full development conditions. Standards 1-year, 24-hour, 2.8 inches of rainfall 2-year, 24-hour, 3.3 inches of rainfall 5-year, 24-hour, 4.1 inches of rainfall 10-year, 24-hour, 5.0 inches of rainfall 105:

30 CHADDS FORD CODE Standards 25-year, 24-hour, 6.0 inches of rainfall 50-year, 24-hour, 6.4 inches of rainfall 100-year, 24-hour, 7.2 inches of rainfall (2) Detention basins shall be designed in accordance with of this chapter. (3) The time of concentration method shall be utilized in the development of the runoff peak discharges. Storage-discharge curves shall be provided for all basins. (4) Meadow condition shall be used as the basis for establishing the predeveloped runoff values for all area other than woodland, including areas which are presently covered by impervious surfaces except as stated below. (5) In the case of an expansion of an existing development, a waiver may be requested from the Board of Supervisors, to exclude only existing impervious areas from the requirements of Subsection Q(1) above, provided that the existing development does not presently contribute to an existing drainage problem downstream. (6) Average antecedent moisture conditions must be used in the formulation of stormwater calculations. (7) A Type II storm distribution be used in the formulation of stormwater calculations. (8) All outlet control structures shall be constructed of galvanized steel, aluminum or concrete, properly anchored to prevent flotation, and equipped with childproof, nonclogging trash racks over all design openings 12 inches or greater in diameter, except those openings designed to carry perennial stream flows. (9) Temporary sedimentation controls shall be provided during construction to prevent the flow of sediment through the basin outlet pipe. Such measures may include temporary riser pipes, rock-filled gabions, plywood stand-boxes, silt fences, and the like. (10) Emergency spillways. Whenever possible, the emergency spillway for basins shall be constructed on undisturbed ground. Emergency spillways shall be constructed of reinforced concrete, vegetated earth, concrete rubble, and the like. All emergency spillways shall be constructed so that the basin berm is protected against erosion. The minimum capacity of all emergency spillways shall be such that the combined capacity of the emergency spillway and the principal from the one-hundred-year design storm after development. Emergency spillways shall extend along the upstream and downstream berm embankment slopes. The emergency spillway shall not discharge stormwater over earthen fill and/or easily erodible material without adequate protection against erosion. (11) Freeboard. The minimum freeboard shall be two feet. (Freeboard is the difference between the design flow elevations in the emergency spillway and the top of the settled basin embankment.) 105:

31 STORMWATER MANAGEMENT (12) Antiseep collars. Antiseep collars shall be installed around the principal pipe barrel within the normal saturation zone of the basin berms. The antiseep collars and their connections to the pipe barrel shall be watertight. The antiseep collars shall extend to a minimum of two feet beyond the outside of the principal pipe barrel. The maximum spacing between collars shall be 14 times the minimum projection of the collar measured perpendicular to the pipe. (13) Basin outlets. Energy dissipating devices (rip-rap, stilling basin, concrete aprons, and the like) shall be placed at all basin outlets. Rock level spreader berms shall be required where basins do not discharge into an existing drainage swale, ditch or channel. Concrete end-walls shall be placed at all basin outlets. All basin outlet pipes 12 inches in diameter or greater shall be equipped with childproof devices. (14) Slope of detention basin embankment. The maximum slope of earthen basin embankments shall be three to one. The top or toe of any slope shall be located a minimum of 15 feet from adjacent property lines with the exception of the downstream property line where the toe of the embankment shall be placed a sufficient distance to allow for energy dissipating devices but in no case less than 30 feet unless approved otherwise by the Township. Whenever possible, the side slopes and basin shape shall blend with the natural topography. Straight side slopes and rectangular basins shall be avoided whenever possible. (15) Width of berm. The minimum top width of detention basin berms shall be 10 feet. (16) Construction specifications. The plans shall indicate the construction specifications and compaction requirements for all detention/retention basins. (17) Slope of basin bottom. In order to insure proper drainage of detention basins, a minimum grade of 2% shall be maintained for all sheet flow. A minimum grade of 1.0% shall be maintained for all channel flow. (18) Cut-off trench. A cut-off trench shall be excavated along the center line of dam on earth fill embankments. The minimum depth shall be three feet. The minimum bottom width shall be 10 feet or wide enough to permit operation of compaction equipment. The side slopes shall be no steeper than one to one. The trench shall be kept free from standing water during the backfilling operations. (19) Overflow system. An overflow system shall be provided to carry flow to the detention basin when the capacity of the storm drain pipe system is exceeded. The overflow system shall be sufficient capacity to carry the difference between the one-hundred year and the ten-year peak flow rates. R. Grading and landscaping of basins. (1) Cuts and fills. No excavation or fill shall be made with a cut or fill slope steeper than three horizontal to one vertical, except where the excavation or fill is sufficiently stable to prevent sliding or erosion and will not result in property damage or personal injury. A written statement shall be required from a civil engineer licensed by the Commonwealth of Pennsylvania having experience in soils engineering certifying that he has inspected the site and that any proposed 105:

32 CHADDS FORD CODE deviation from the slope specified above should not endanger any property or result in personal injury. Retaining walls will be required if a stable slope cannot be maintained. Any retaining wall design must be designed by an experienced structural engineer licensed by the Commonwealth of Pennsylvania and approved by the Township. The toe of any cut or fill slope must be located a minimum of 15 feet from adjacent property lines with the exception stated above. (2) Retention/detention basins shall be designed to utilize the natural contours of the land whenever possible. When such design is impracticable, the construction of basin shall utilize slopes as shallow as possible to blend the structures into the terrain. (3) A minimum of six inches of topsoil shall be placed on all areas affected by the basin construction (bottom of basin, side slopes, top of berm, and the like). (4) All earthen basins shall be stabilized with temporary and permanent grasses or other approved ground covers within 15 days after initial construction. (5) Fencing and/or a suitable vegetation screening shall be provided around all detention/retention basins unless the Board of Supervisors determines that such screening is not necessary. (6) Basins shall be installed prior to any earthmoving or land disturbances, which they will serve. S. Subsurface disposal of stormwater. (1) Subsurface disposal of stormwater shall be allowed only where natural, well-drained soils exist and only after on-site soil percolation tests, certified by a registered professional engineer experienced in soils engineering, geologist, qualified soils scientist, and the like, are performed. (2) Soils testing to determine percolation rates shall be performed at several locations where the subsurface facility is proposed and also at the proposed invert elevation of the subsurface facility. (3) All percolation tests shall be conducted in accordance with the rules, regulations and procedures of the Pennsylvania Sewage Facilities Act (Act 537) 14 as required by the Pennsylvania Department of Environmental Protection. (4) Various methods of subsurface disposal may be employed. The effectiveness and applicability of each should be evaluated at each location. Acceptable methods include, but are not limited to, infiltration basins and/or berms, seepage beds and/or trenches, and the like. (5) The design and construction of all subsurface facilities shall provide proper procedures to prevent silt from clogging the aggregate backfill. 14. Editor's Note: See 35 P.S et seq. 105:

33 STORMWATER MANAGEMENT (6) The following procedures and materials shall be required for all subsurface facilities: (a) (b) (c) (d) (e) (f) (g) Excavation for the infiltration facility shall be performed with equipment which will not compact the bottom of the seepage bed/trench, or like facility. The bottom of the bed and/or trench shall be scarified prior to the placement of aggregate. Only clean aggregate, free of fines, shall be allowed. The top and sides of all seepage beds, trenches, or like facilities shall be covered with drainage filtration fabric. Perforated distribution pipes connected to centralized catch basins and/or manholes with provisions for the collection of debris shall be provided in all facilities. The perforated pipes shall distribute stormwater throughout the entire seepage bed/trench, or like facility. A positive outlet pipe placed at or near the bottom of the seepage bed and/or trench, or like facility, shall be provided. The landowner or developer shall be responsible for the proper installation, operation and maintenance of all subsurface stormwater management facilities. If, in the opinion of the Township, the underground system is not functioning properly, the landowner or developer shall be required to make the necessary improvements/corrections to the system or provide an alternate stormwater management facility which is functional. T. Storm sewer system design. (1) Design flow rate. The storm sewer system shall be designed to carry a fifty-year peak flow rate, with a one-hundred-year peak flow rate at all low points. The peak flow rate into each inlet shall be indicated on the stormwater drainage stormwater management plan. The design flow rate shall be determined by the rational formula, Q=CIA. (2) Pipe material and gage thickness. All storm sewers shall be either reinforced cement concrete, corrugated aluminum, corrugated galvanized steel pipe or high density polyethylene pipe (HDPE). Storm sewers shall be of the proper class and thickness to support the above fill material. Pipe class and gage or thickness shall be noted on the plans. (3) Allowable headwater depth. At all inlets or manholes, the maximum allowable headwater depth shall be one foot below the top of the inlet grate or the manhole cover. (4) Horizontal pipe deflections. A manhole or inlet shall be provided at all horizontal deflections in the storm pipe system exceeding 5. (5) Minimum and maximum cover. A minimum of 18 inches of cover shall be maintained over all storm drain pipes. The top of storm drain pipes shall be at least 105:

34 CHADDS FORD CODE foot below subgrade elevation. The maximum cover over storm drain pipes shall be 10 feet unless approved otherwise by the Township. (6) Storm sewer system outlets. Storm sewer system outlet pipes shall extend to proposed stormwater management facilities, natural watercourses, and the like. A concrete endwall shall be required on all storm sewer system outlet pipes. (7) Roof drains. Stormwater roof drains shall not discharge water directly over a sidewalk, into any sanitary sewer line, or into a street or paved area without a straight curbed gutter. (8) The storm sewer system shall be designed to the more restrictive of the following: to collect stormwater at any point where three to five cubic feet per second is accumulated during the design storm; and/or inlets/manholes shall not be spaced more than 300 feet apart on pipe sizes up to 24 inches in diameter and not more than 400 feet apart on greater sizes. (9) Inlets, manholes, grates, covers, frames, and the like shall conform to the Pennsylvania Department of Transportation Roadway Construction Standards (Publication No. 72) and Form 408 Specifications, and all amendments, revisions or updates thereto. (10) Bridges and culverts shall have ample waterway to carry expected flows, based on minimum storm frequency of 25 years, PennDOT bridge and culvert specifications and/or the Pennsylvania Department of Environmental Protection requirements. All culverts shall be provided with concrete end sections unless approved otherwise by the Township. 15 (11) All drainage channels shall be designed to carry a flow rate equal to a one-hundred-year, twenty-four-hour storm. (12) All drainage channels shall be designed to prevent the erosion of the bed and bank areas. The flow velocity in all vegetated drainage channels shall not exceed the maximum permissible velocity to prevent erosion. Suitable bank stabilization shall be provided where required to prevent erosion of the drainage channels. Where storm sewers discharge into existing drainage channels at an angle greater than 30 from parallel with the downstream channel flow, the far side bank shall be stabilized by the use of rip-rap, masonry, and/or concrete walls. The stabilization shall be designed to prevent erosion and frost heave under and behind the stabilizing media. (13) Any vegetated drainage channel requiring mowing of the vegetation shall have a maximum slope of three horizontal to one vertical on those areas to be mowed. (14) Inlet capacity. All inlets must be designed to accommodate the ten-year peak flow rate except at low points where they shall accommodate the twenty-five-year peak flow rate. 15. Editor's Note: Amended at time of adoption of Code (see Ch. 1, General Provisions, Art. II). 105:

35 STORMWATER MANAGEMENT (15) Straight pipe sections. Wherever possible, all storm sewers shall be designed to follow straight courses. No angular deflections of storm sewer pipe sections in excess of 5 shall be permitted. No vertical curves shall be permitted in the storm sewer system. (16) Minimum grade and size. All storm drain pipes shall be designed to maintain a minimum grade of 1.0%. All storm sewer pipes shall have a minimum inside diameter of 15 inches. (17) Pipe arches. Where headroom is restricted, equivalent pipe arches may be used in lieu of circular pipes Erosion and sedimentation requirements. A. Whenever the vegetation and topography are to be disturbed, such activity must be in conformance with Chapter 102, Title 25, Rules and Regulations, Part 1, Commonwealth of Pennsylvania, DEP, Subpart C, Protection of Natural Resources, Article II, Water Resources, Chapter 102, "Erosion Control," and in accordance with the Delaware County Conservation District, as appropriate, and the standards and specifications of the appropriate municipal government. B. Additional erosion and sedimentation control design standards and criteria that must be applied where infiltration BMPs are proposed include the following: (1) Areas proposed for infiltration BMPs shall be protected from sedimentation and compaction during the construction phase to maintain their maximum infiltration capacity. (2) In order to ensure compliance with Chapter 102, the timing of the installation and operation of the infiltration BMP shall be at the discretion of the Municipal Engineer. C. Soil erosion and sedimentation control; general regulations. (1) All subdivisions and land developments are required to comply with the Clean Streams Law of Pennsylvania 16 and Chapter 102 of the Rules of Regulations of the Pennsylvania Department of Environmental Protection, as amended from time to time. (2) The landowner or developer shall be responsible for the submission and approval of an application to the regional office of the Pennsylvania Department of Environmental Protection for a permit to allow any earthmoving activity where more than 25 acres are disturbed at one time. All landowners or developers are required to obtain such permit except as otherwise provided in Section , Permits and Plans, of Chapter 102 of the Rules and Regulations of the 16. Editor's Note: See 35 P.S et seq. 105:

36 CHADDS FORD CODE Pennsylvania Department of Environmental Protection (DEP), as amended from time to time. 17 (3) The soil erosion and sedimentation control plan must be available at all times at the construction site. The permit allowing earthmoving activity shall be obtained by the landowner or developer before any construction on the site shall begin. (4) The sequence of soils stabilization to control soil erosion and sedimentation shall be planned so as to compensate for seasonal effects such as the inability to establish vegetation during winter months, the influence of freezing, and the like. (5) Measures shall be taken to preclude the tracking of mud, soil and the like from construction vehicles and equipment onto streets which serve the site. Such measures shall include temporary scrub pads with collector sumps and cleaning devices, which construction vehicles shall pass through prior to leaving the site. (6) Erosion and sedimentation control measures. (a) Measures used to control erosion and reduce sedimentation shall as a minimum meet the latest revised standards, specifications and/or regulations of: [1] U.S. Department of Agriculture Soil Conservation Service as adopted by the Delaware County Conservation District in its Erosion and Sediment Control Handbook. [2] Commonwealth of Pennsylvania Department of Environmental Protection in its Soil Erosion and Sedimentation Control Manual. [3] "Standards and Specifications for Soil Erosion and Sediment Control in Developing Areas" by the U.S. Department of Agriculture, Soil Conservation Service, College Park, Maryland. (b) Erosion and sedimentation control measures shall be required on all erosion and sedimentation control and stormwater management plans for all subdivisions and/or land developments within the Township. The Township or its designated representative shall ensure and enforce compliance with the appropriate standards. (7) All soil erosion and sedimentation control and grading activities shall be performed in such a manner so as not to endanger or damage public or private property or to cause physical damage or personal injury. A landowner or developer shall be responsible for any property damage or personal injury caused by his activities. (8) There shall be no increase in discharge of sediment or other solid materials from the site as a result of stormwater runoff; and, in the event of any increase, the landowner and/or developer shall be responsible. 17. Editor's Note: Amended at time of adoption of Code (see Ch. 1, General Provisions, Art. II). 105:

37 STORMWATER MANAGEMENT (9) Soil erosion and sedimentation control devices, such as temporary vegetation and mulch, temporary earthen berms, interceptor dikes, ditches, diversion terraces, rock filter berms, crushed stone tire scrubbers, silt basins, silt fences, and the like, appropriate to the scale of operations, shall be installed concurrent with earthmoving activities and whenever any situation is created which would contribute to increased erosion. (10) Earthmoving operations shall be minimized where possible and practicable to preserve desirable natural features and the topography of the site. (11) Stripping of vegetation, regrading or other development shall be done in such a way that will minimize erosion. (12) To the maximum extent possible, mature, healthy trees of 12 inches or greater in caliper and other significant existing vegetation shall be retained and protected. Such trees shall not be removed, except as provided on the approved subdivision and/or land development plan. The filling of soil more than five inches is presumed to extend out from the tree as far as the tree's branches extend outward. (13) Land disturbance shall be limited to the actual construction site and an access strip. The amount of disturbed area and the duration of exposure shall be kept to a practical minimum. Disturbed areas shall be stabilized with vegetation, mulch, erosion control fabric, and the like as soon as possible after earthmoving procedures. (14) Provisions shall be made to effectively accommodate the increased runoff caused by changed soil and surface conditions during and after development. Water runoff shall be minimized and retained on-site wherever possible to facilitate groundwater recharge. (15) Temporary vegetation and/or mulching shall be used to protect critical areas during development. (Critical areas shall be construed to mean those portions of the site which are extremely vulnerable to soil erosion.) (16) The permanent final vegetation and structural erosion control and drainage measures shall be installed as soon as practical in the development in accordance with the approved plans. (17) Sediment in the runoff water shall be trapped until the disturbed area is stabilized by the use of debris and sediment basins, silt fences or other approved measures. Sediment deposits in basins, silt fences, and the like shall be removed at periodic intervals during the construction period, as directed by the Township. (18) Procedures shall be established for protecting soils and rock or geologic formations with water supply potential from contamination by surface water or other source or disruption caused by construction activity. (19) Silt fences shall be utilized in lieu of straw bale silt barriers downhill of all construction areas. In general, straw bale silt barriers will be allowed only on projects with a construction period of less than 60 days and where the uphill 105:

38 CHADDS FORD CODE drainage area is less than 1/2 acre. In all applications, silt fences and straw bale silt barriers shall be securely anchored in place and embedded into the soil. (20) Silt fences or silt traps shall be placed at all inlets, headwalls, basin outlets and similar drainage structures during the construction period in order to prevent sediment from entering any watercourse, storm drainage system, or other areas downstream. (21) Crushed stone tire scrubbers shall be placed at all entrances to construction areas. Tire scrubbers shall be sufficient width and length to prevent the transportation of sediment off of the construction site. (22) Temporary and permanent seeding and mulch specifications shall be noted on all plans. The specifications shall include lime and fertilizer rates of application, as well as other provisions regarding procedures and materials. In critical areas, the Township may require hydroseeding. (23) During roadway grading, interceptor dikes shall be installed on all roadway subgrades with slopes in excess of 5% to prevent erosion of the subgrade. The interceptor dikes shall divert stormwater runoff into silt traps or silt fences. (24) The crushed stone base course for driveways, roadways and parking areas shall be applied as soon as possible after grading procedures, in order to prevent erosion of the subgrade. (25) Drainage swales and ditches, and all slopes greater than three to one, shall be protected against erosive velocities with erosion control measures such as erosion control fabric and other material as approved by the Township. (26) Energy dissipators and/or stilling basins shall be installed at the outlet end of all storm drainage facilities. (27) Whenever sedimentation is caused by stripping vegetation, regrading or other development, it shall be the responsibility of the person causing such sedimentation to remove the accumulated sediment from all adjoining or downstream properties, surfaces, drainage systems and watercourses and to repair any damage at his expense as quickly as possible. (28) All necessary soil erosion and sediment control measures installed under this chapter shall be adequately maintained by the developer after completion of the approved plan or until such measures are permanently stabilized as determined by the Township. (29) In any construction in the Township, no construction trash, trees or parts of trees or any foreign material shall be buried at the site. Each contractor shall maintain a facility wherein all trash shall be deposited and thereafter removed from the site to an approved landfill. In the case of placement of fill, all fill must be approved by the Code Enforcement Officer prior to placement of the same. Any contractor desiring to place fill other than the natural earth on the site shall notify the Code Enforcement Officer and request an inspection. 105:

39 STORMWATER MANAGEMENT ARTICLE V Inspections Schedule of inspections. A. The Municipal Engineer or his municipal assignee shall inspect all phases of the installation of the permanent stormwater management and water quality facilities, including nonstructural BMPs. B. During any stage of the work, if the Municipal Engineer determines that the permanent stormwater management facilities, water quality facilities, or nonstructural BMPs are not being installed in accordance with this chapter, the municipality shall revoke any existing municipal permits or issue a stop-work order until a revised drainage plan is submitted and approved, as specified in this chapter. ARTICLE VI Fees and Expenses General provisions. The fee required by this chapter is the municipal review fee. The municipal review fee shall be established by the municipality to defray review costs incurred by the municipality and the Municipal Engineer. All fees shall be paid by the applicant Municipal stormwater management plan review fee. The municipality shall establish a review fee schedule by separate resolution of the municipal governing body based on the size of the regulated activity and based on the municipality's costs for reviewing stormwater management plans. The municipality may periodically update the review fee schedule to ensure that review costs are adequately reimbursed Expenses covered by fees. The fees required by this chapter shall, at a minimum, cover: A. Administrative costs. B. The review of the stormwater management plan by the municipality and the Municipal Engineer. C. The site inspections. D. The inspection of stormwater management facilities and stormwater management improvements during construction. E. The final inspection upon completion of the stormwater management facilities and drainage stormwater management improvements presented in the stormwater management plan. 105:

40 CHADDS FORD CODE Additional costs. The applicant will be invoiced for any additional costs incurred by the municipality in the course of reviewing the development plan. These costs may include, but are not limited to, special studies by qualified engineers or surveyors, field reconnaissance, and testing. ARTICLE VII Maintenance Responsibilities Performance guarantee. The applicant shall provide a financial guarantee to the municipality for the timely installation and proper construction of all stormwater management controls as required by the approved stormwater plan and this chapter equal to the full construction cost of the required controls Maintenance responsibilities. A. The stormwater management plan for the development site shall contain an operation and maintenance plan prepared by the applicant and approved by the Municipal Engineer. The operation and maintenance plan shall outline required routine maintenance actions and schedules necessary to ensure proper operation of the facilities. B. The stormwater management plan for the development site shall establish responsibilities for the continued operation and maintenance of all proposed stormwater control facilities, consistent with the following principles: (1) If a development consists of structures or lots that are to be separately owned and in which streets, sewers, and other public improvements are to be dedicated to the municipality, stormwater control facilities may also be dedicated to and maintained by the municipality. (2) If a development site is to be maintained in single ownership or if sewers and other public improvements are to be privately owned and maintained, then the ownership and maintenance of stormwater control facilities shall be the responsibility of the owner or private management entity. C. The municipality, upon recommendation of the Municipal Engineer, shall make the final determination on the continuing maintenance responsibilities prior to final approval of the stormwater management plan. The municipality reserves the right to accept the ownership and operating responsibility for any or all of the stormwater management controls Maintenance agreement for privately owned stormwater facilities. A. Prior to final approval of the site's stormwater management plan, the property owner shall sign and record a maintenance agreement covering all stormwater control facilities 105:

41 STORMWATER MANAGEMENT that are to be privately owned. Said agreement, designated as Appendix E, is attached and made a part hereto. 18 B. Other items may be included in the agreement where determined necessary to guarantee the satisfactory maintenance of all facilities. The maintenance agreement shall be subject to the review and approval of the Municipal Solicitor and municipality Postconstruction maintenance inspections. A. Stormwater detention and retention basins or facilities shall be inspected by, or under the direction of, a registered professional engineer on behalf of the applicant or responsible entity (including the Municipal Engineer for dedicated facilities) on the following basis: (1) Annually for the first five years. (2) Once every three years thereafter. (3) During or immediately after the cessation of a one-hundred-year or greater storm event. B. The entity conducting the inspection shall be required to submit a report to the municipality within one month following completion of the inspection. The report will present documentation regarding the condition of the facility and recommend necessary repairs, if needed. Any needed repairs shall be implemented by the owner within one month of the report issuance date. ARTICLE VIII Prohibitions Prohibited discharges. A. No person in the municipality shall allow or cause to allow stormwater discharges into the municipality's separate storm sewer system which are not composed entirely of stormwater, except discharges allowed under a state or federal permit. B. Discharges which may be allowed under the municipality's NPDES permit based on a finding by the municipality that the discharge(s) do not significantly contribute to pollution to surface waters of the commonwealth by the municipality are: (1) Water line flushing. (2) Landscape irrigation. (3) Diverted stream flows. (4) Rising groundwaters. (5) Uncontaminated pumped groundwater. 18. Editor's Note: Appendix E is on file in the Township offices. 105:

42 CHADDS FORD CODE (6) Springs. (7) Water from crawl space pumps. (8) Footing drains. (9) Dechlorinated swimming pool discharges. (10) Discharges from potable sources. (11) Discharges from foundation drains. (12) Air-conditioning condensation. (13) Irrigation water. (14) Flows from riparian habitats and wetlands. (15) Street wash water. (16) Individual residential car washing. (17) Lawn watering. (18) Discharges from fire-fighting activities, including training. C. In the event that the municipality subsequently determines that any of the discharges identified in Subsection B significantly contribute to pollution of waters of the commonwealth by the municipality, then the municipality will notify the responsible person to cease the discharge. D. Upon notice provided by the municipality under Subsection C, the discharger will have a reasonable time to cease the discharge consistent with the degree of pollution caused by the discharge Prohibited connections. A. The following connections are prohibited: (1) Any drain or conveyance, whether on the surface or subsurface, which allows any nonstormwater discharge including sewage, process wastewater, and wash water to enter the separate storm sewer system, and any connections to the storm drain system from indoor drains and sinks. (2) Any drain or conveyance connected from a commercial or industrial land use to the separate storm sewer system which has not been documented in plans, maps, or equivalent records, and approved by the municipality. B. This prohibition expressly includes, without limitation, connections made in the past, regardless of whether the connection, drain or conveyance was previously allowed, permitted, or approved by a government agency, or otherwise permissible under law or practices applicable or prevailing at the time of connection. 105:

43 STORMWATER MANAGEMENT Roof drains. A. Roof drains shall not be connected to streets, sanitary or storm sewers or roadside ditches, except as provided in B. B. When it is more advantageous to connect directly to streets or storm sewers, connections of roof drains to streets or roadside ditches may be permitted on a case-by-case basis by the municipality. C. Roof drains shall discharge to infiltration areas or vegetative BMPs to the maximum extent practicable Waste disposal prohibitions. No person shall throw, deposit, leave, maintain, keep, or permit to be thrown, deposited, left, or maintained, in or upon any public or private property, driveway, parking area, street, alley, sidewalk, or other component of the municipality's separate storm sewer system, any refuse, rubbish, garbage, litter, or other discarded or abandoned objects, articles, and accumulations, so that the same may cause or contribute to pollution. Wastes deposited in streets in proper waste receptacles for the purposes of collection are exempted from this prohibition Alteration of BMPs. A. No person shall modify, remove, fill, landscape or alter any existing stormwater BMP, unless part of an approved maintenance program, without the written approval of the municipality. B. No person shall place any structure, fill, landscaping or vegetation into a stormwater BMP or within a drainage easement, which would limit or alter the functioning of the BMP, without the written approval of the municipality. ARTICLE IX Enforcement and Penalties Right of entry. Upon presentation of proper credentials, duly authorized representatives of the municipality may enter at reasonable times upon any property within the municipality to inspect the condition of the stormwater structures and facilities in regard to any aspect regulated by this chapter Notices of violations. In the event that a person fails to comply with the requirements of this chapter or fails to conform to the requirements of any permit issued hereunder, the municipality shall provide written notification of the violation. Such notification shall set forth the nature of the violation(s) and establish a time limit for correction of the violation(s). Failure to comply within the time specified shall subject such person to the penalty provision of this chapter. All 105:

44 CHADDS FORD CODE such penalties shall be deemed cumulative and shall not prevent the municipality from pursuing any and all other remedies. It shall be the responsibility of the owner of the real property on which any regulated activity is proposed to occur, is occurring, or has occurred, to comply with the terms and conditions of this chapter Enforcement; additional project requirements. The municipality is hereby authorized and directed to enforce all of the provisions of this chapter. All inspections regarding compliance with the stormwater management plan shall be the responsibility of the Municipal Engineer or other qualified persons designated by the municipality. A. A set of design plans approved by the municipality shall be on file at the site throughout the duration of the construction activity. Periodic inspections may be made by the municipality or designee during construction. B. It shall be unlawful for any person, firm, or corporation to undertake any regulated activity under on any property except as provided for in the approved stormwater management plan and pursuant to the requirements of this chapter. It shall be unlawful to alter or remove any control structure required by the stormwater management plan and pursuant to this chapter or to allow the property to remain in a condition that does not conform to the approved stormwater management plan. C. At the completion of the project, and as a prerequisite for the release of the performance guarantee, the owner or his representatives shall: (1) Provide a certification of completion from an engineer, architect, surveyor, or other qualified person verifying that all permanent facilities have been constructed according to the plans and specifications and approved revisions thereto. (2) Provide a printed set of as-built drawings to the municipality. (3) Provide a set of as-built drawings to the County Conservation District. Such plans shall be prepared in accordance with established criteria and procedures and in a format (electronic or otherwise) as required by the Conservation District for long-term storage. D. After receipt of the certification by the municipality, a final inspection shall be conducted by the governing body or its designee to certify compliance with this chapter. E. Suspension and revocation of permits. (1) Any municipal permit issued under this chapter may be suspended or revoked or a stop-work order may be issued by the municipality for: (a) (b) Noncompliance with or failure to implement any provision of the permit. A violation of any provision of this chapter or any other applicable law, ordinance, rule, or regulation relating to the project. 105:

45 STORMWATER MANAGEMENT (c) The creation of any condition or the commission of any act during construction or development which constitutes or creates a hazard or nuisance, or which endangers the life or property of others. (2) Reinstatement of permits. (a) A suspended permit shall be reinstated by the municipality when: [1] The Municipal Engineer or his designee has inspected and approved the corrections to the stormwater management and erosion and sediment pollution control measure(s); and/or [2] The municipality is satisfied that the violation of the ordinance, law, or rule and regulation has been corrected. (b) A permit that has been revoked by the municipality cannot be reinstated. The applicant may apply for a new permit under the procedures outlined in this chapter. F. Occupancy permit. An occupancy permit shall not be issued by the municipality unless all requirements of this chapter have been met. The occupancy permit shall be required for each lot owner and/or applicant for all subdivisions and land development in the municipality Violation deemed a public nuisance. A. The violation of any provision of this chapter is hereby deemed a public nuisance. B. Each day that a violation continues shall constitute a separate violation Violations and penalties; additional remedies. A. Anyone violating the provisions of this chapter shall be subject to a fine for each violation plus court costs and attorney fees. Each day that the violation continues shall be a separate offense. B. In addition, the municipality, through its Solicitor, may institute injunctive, mandamus, or any other appropriate action or proceeding at law or in equity for the enforcement of this chapter. Any court of competent jurisdiction shall have the right to issue restraining orders, temporary or permanent injunctions, mandamus, or other appropriate forms of remedy or relief Appeals. A. Any person aggrieved by any action of the municipality or its designee, relevant to the provisions of this chapter, may appeal to the municipality within 30 days of that action. 105:

46 CHADDS FORD CODE B. Any person aggrieved by any decision of the municipality, relevant to the provisions of this chapter, may appeal to the County Court of Common Pleas in the county where the activity has taken place within 30 days of the governing body's decision. 105:

47 STORMWATER MANAGEMENT 105 Attachment 1 Chadds Ford Township Figure 4-1 Water Quality and Quantity Control Drainage Plan Preparation Procedure DETERMINE IF PROJECT MEETS EXEMPTION CRITERIA PROCEED TO DRAINAGE PLAN PREPARATION STEP 1 - INFILTRATE STEP 2 - EXTENDED DETENTION STEP 3 - ADDITIONAL DESIGN CONTROLS Does project meet exemption criteria in 105-9? Yes Proceed to development in accordance with local regulations. No Implement riparian buffer requirements from A(2), if applicable. Applicant determines if development meets definition of Redevelopment per Article II. Yes Applicant adjusts predevelopment RCN or C value based on curves presented in C and Appendix B. No Provide infiltration facilities in areas of suitable soil from all impervious surfaces. Volume of storage shall be no less than the net increase in runoff from the 2-year storm event, or 1 inch of runoff from the total area draining to the infiltration facility, whichever is greater. Does post development peak discharge for all design storms meet control criteria for stormwater management districts? [ through ] Yes STOP - Applicant may submit drainage plan to municipality subject to Article III. No Reduce impervious cover through better site design. Repeat Step 1 Detain the 2-year, 24-hour design storm runoff based on SCS type II distribution for at least 24 hours. The volume of infiltration provided for the contributing area from Step 1 may be deducted from the volume requirement for extended detention. [ A(3)] No Does post development peak discharge for all design storms meet control criteria for stormwater management districts? [ through ] Does post development peak discharge for all design storms meet control criteria for stormwater management districts? [ through ] Yes STOP - Applicant may submit drainage plan to municipality subject to Article III. No Implement other design controls to meet peak discharge and volume control requirements for stormwater management districts. See Article IV. Does post development peak discharge for all design storms meet control criteria for stormwater management districts? [ through ] No Yes STOP - Applicant may submit drainage plan to municipality subject to Article III. Yes Repeat Steps 1-3 until stormwater management controls are met in accordance with Ordinance and consistent with Chester Creek Stormwater Management Plan. STOP - Applicant may submit drainage plan to municipality subject to Article III. 105 Attachment 1:

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